Meprin ? and are members of a superfamily of metzincin proteases implicated in systemic sclerosis. Studies indicate that the overexpression of meprin ? and is correlated with increased deposition of fibrillar collagens in skin and other organs and tissues. This can potentially lead to kidney, lung, and heart fibrosis and eventual failure and death. The main obstacle in studying the roles of meprin ? and in systemic sclerosis is the lack of selective inhibitors. Most of the meprin ? and inhibitors developed t date feature Zn-binding moieties that target the active site Zn. There are approximately 70 known human metalloproteases that have Zn in their active site, which leads to an off-target toxicity of Zn-binding inhibitors. Based on our preliminary results, we hypothesize that meprin and selective inhibitors will be effective research tools in systemic sclerosis where meprin ? and are implicated. There are currently no publicly available selective inhibitors of meprin ? and metalloproteases. The overall aim of this project is to develop selective inhibitors of meprin ? and . The specific aims of this proposal will focus on (1) High throughput screening (HTS) of the Scripps library which consists of > 640,000 compounds; (2) Medicinal chemistry and in vitro characterization of selective probes of meprin ? and . Our laboratory is uniquely positioned to achieve these goals due to expertise in biology, biochemistry and drug/probe discovery for metalloproteases. We discovered a novel class of metalloprotease ADAM17 inhibitors that spare its closest analogue, ADAM10, and most common anti-targets (MMP-14 and -8). To our knowledge, we are the first laboratory to report ADAM17 inhibitors with such unique selectivity. Additionally, we discovered novel selective non-zinc-binding inhibitors of another metalloprotease, MMP-13, implicated in osteoarthritis. Most germane to the present proposal, both discoveries were made utilizing HTS either of NIH or TPIMS libraries in close collaboration with Scripps Research Institute Molecular Screening Center (co-headed by Dr. Louis Scampavia and Mr. Tim Spicer) and Dr. Gregg Fields. We strongly believe that HTS of Scripps library will result in the discovery of much needed first-in-class selective inhibitors of meprin ? and . We will also collaborate with experts in the fields of peptide synthesis, HTS, and medicinal chemistry. Our expected outcome is a clear understanding of the role of meprin ? and in systemic sclerosis, which will lead to a more comprehensive knowledge of the mechanisms that regulate its progression and potentially result in the development of novel therapies.